BETHESDA, Md. -- The growing number of cosmetics, drugs other products made using nanotechnology need more attention from U.S. regulators to make sure they are safe for humans and the planet, consumer and environmental groups told a government hearing Tuesday.

Nanotechnology is the design and use of particles as small as one-billionth of a meter. A human hair, by contrast, is about 80,000 nanometers across.

Materials at nano-size can have completely different properties from larger versions, such as unusual strength or the ability to conduct electricity.

Witnesses at a meeting called by the U.S. Food and Drug Administration agreed nanotechnology holds promise for a vast range of products, including new medicines to treat diseases or delivery systems to get drugs to body parts now hard to reach.

But some complained that dozens of cosmetics and a handful of drugs made with nanomaterials already have made it to the market while regulators have done little to track their use or safety.

"Unfortunately, so far the U.S. government has acted as a cheerleader, not a regulator, in addressing the nanotech revolution. Health and environmental effects have taken a back seat," said Kathy Jo Wetter of ETC Group, an organization that tracks the impact of new technologies.

The FDA has treated products made with nanotechnology the same way it handles others. For drugs with nanomaterials, that means companies must provide evidence of safety and effectiveness before they reach the market. But cosmetics, foods and dietary supplements are not subject to FDA oversight before they are sold -- with or without nanoparticles.

While no harm has been documented, concerns have arisen that the tiny particles are unpredictable and could have unforeseen impacts in the human body or in the environment.

As they called for close FDA oversight, many experts said they felt the agency was ill-equipped to regulate the new technology in the midst of other responsibilities.

"New nano-enabled drugs and medical devices ... place burdens on an oversight agency that is already stretched extremely thin," said David Rejeski, director of the Project on Emerging Nanotechnologies, a group aimed at helping society anticipate and manage effects of nanotechnology.

The FDA has created an internal task force on nanotechnology, and officials said they called the meeting to learn what scientific issues the agency should address.

The task force is due to report to the commissioner in nine months, said Dr. Randall Lutter, FDA's associate commissioner for policy and planning.

"It's not only the risks, it's also looking at the potential. There's a lot of opportunity... to bring great things to patients," he said at the meeting.

Industry groups and some other experts urged the agency not to overreact.

"The key is to manage the risk while achieving the maximum benefit from these materials. It would be wrong for us to over-regulate," said Martin Philbert of the University of Michigan School of Public Health.